The present invention is directed to digital electronic circuits and, more particularly, to a voltage level shifter.
A semiconductor device, such as an integrated circuit (IC) may operate using more than one power supply voltage. For example, an IC may have internal modules having different functions and using different power supply voltages. Further, the signal level at an input/output terminal connected to an external module may be determined for compatibility with the characteristics of the connected module and require a power supply voltage different from that for internal circuits. A level shifter (sometimes also referred to as a level translator) is a widely used circuit used to convert signal levels to a higher or lower voltage.
Two key parameters of a level shifter are its current and power consumption, and its transfer delay (the delay between a change in the input signal and a corresponding change in the output signal. The power supply voltage for a level shifter is high, often being the highest voltage in the IC, making low current consumption a particularly important parameter for low power consumption. Transfer delay is also important, especially in some gate driver applications that need a fast turning on time. These parameters tend to be conflicting and known level shifters represent a compromise between the two parameters. It is desirable to provide a level shifter with lower consumption current but also with higher transfer speed.